1. Field of the Invention
The present invention relates to an asynchronous transfer mode (ATM) multiplex transmission system having test equipment which performs load tests etc. on the incoming or outgoing first-in first-out (FIFO) memories used for an ATM cross connection processing unit.
In recent years, attention has focused on ATM type telecommunications equipment, which divides a series of information into cells of any finite length and transmits these cells so as to make more efficient use of telecommunication channels. The ATM system is a new technology and therefore there are currently no established tests for the load of the FIFO memories used for the ATM cross connection processing units. Various methods are being proposed at this stage.
2. Description of the Related Art
As explained later in detail, various types of ATM multiplex transmission apparatuses have already been proposed, but in all of these types of ATM multiplex transmission apparatuses, provision is made, as an external apparatus, of a load feeding apparatus which generates test use dummy cells for load tests simulating overload states, constant load states, etc. of the incoming or outgoing FIFO memories of the ATM cross connection processing unit. These dummy cells generated by the load feeding apparatus (for example, dummy cells which concentrate at a particular outgoing channel) are fed to the ATM multiplex transmission apparatus for testing the same. Here, the above-mentioned external apparatus means an apparatus which is outside of the ATM multiplex transmission apparatus and, for example, is an apparatus provided near the subscriber's terminal equipment.
There was the following problem, however, in a test of an ATM cross connection processing unit using the above-mentioned conventional load test equipment.
When the amount of processing of an ATM multiplex transmission apparatus is large (for example, when the capacity of the incoming or outgoing FIFO memories is large), it is necessary to input large amounts of dummy cells from the incoming channel of an adaptation ATM layer (AAL) processing unit to perform the above-mentioned test. Therefore, since the processing capacity of the AAL processing unit (capacity of amount of cells which can be received) is limited, it is not enough to input dummy cells from just a single line, that is, it is necessary to prepare a large number of load feeding apparatuses and input dummy cells from a large number of incoming lines. As a result, a large test environment was required.
Further, in the transitional period before the spread of ATM systems, the chances are high that load characteristic dedicated measuring apparatuses will not be available, so some sort of suitable measurement method must be proposed until they become available.